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| 1 | +######################## BEGIN LICENSE BLOCK ######################## |
| 2 | +# The Original Code is Mozilla Communicator client code. |
| 3 | +# |
| 4 | +# The Initial Developer of the Original Code is |
| 5 | +# Netscape Communications Corporation. |
| 6 | +# Portions created by the Initial Developer are Copyright (C) 1998 |
| 7 | +# the Initial Developer. All Rights Reserved. |
| 8 | +# |
| 9 | +# Contributor(s): |
| 10 | +# Mark Pilgrim - port to Python |
| 11 | +# |
| 12 | +# This library is free software; you can redistribute it and/or |
| 13 | +# modify it under the terms of the GNU Lesser General Public |
| 14 | +# License as published by the Free Software Foundation; either |
| 15 | +# version 2.1 of the License, or (at your option) any later version. |
| 16 | +# |
| 17 | +# This library is distributed in the hope that it will be useful, |
| 18 | +# but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 19 | +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 20 | +# Lesser General Public License for more details. |
| 21 | +# |
| 22 | +# You should have received a copy of the GNU Lesser General Public |
| 23 | +# License along with this library; if not, write to the Free Software |
| 24 | +# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA |
| 25 | +# 02110-1301 USA |
| 26 | +######################### END LICENSE BLOCK ######################### |
| 27 | + |
| 28 | +from .euctwfreq import (EUCTW_CHAR_TO_FREQ_ORDER, EUCTW_TABLE_SIZE, |
| 29 | + EUCTW_TYPICAL_DISTRIBUTION_RATIO) |
| 30 | +from .euckrfreq import (EUCKR_CHAR_TO_FREQ_ORDER, EUCKR_TABLE_SIZE, |
| 31 | + EUCKR_TYPICAL_DISTRIBUTION_RATIO) |
| 32 | +from .gb2312freq import (GB2312_CHAR_TO_FREQ_ORDER, GB2312_TABLE_SIZE, |
| 33 | + GB2312_TYPICAL_DISTRIBUTION_RATIO) |
| 34 | +from .big5freq import (BIG5_CHAR_TO_FREQ_ORDER, BIG5_TABLE_SIZE, |
| 35 | + BIG5_TYPICAL_DISTRIBUTION_RATIO) |
| 36 | +from .jisfreq import (JIS_CHAR_TO_FREQ_ORDER, JIS_TABLE_SIZE, |
| 37 | + JIS_TYPICAL_DISTRIBUTION_RATIO) |
| 38 | + |
| 39 | + |
| 40 | +class CharDistributionAnalysis(object): |
| 41 | + ENOUGH_DATA_THRESHOLD = 1024 |
| 42 | + SURE_YES = 0.99 |
| 43 | + SURE_NO = 0.01 |
| 44 | + MINIMUM_DATA_THRESHOLD = 3 |
| 45 | + |
| 46 | + def __init__(self): |
| 47 | + # Mapping table to get frequency order from char order (get from |
| 48 | + # GetOrder()) |
| 49 | + self._char_to_freq_order = None |
| 50 | + self._table_size = None # Size of above table |
| 51 | + # This is a constant value which varies from language to language, |
| 52 | + # used in calculating confidence. See |
| 53 | + # http://www.mozilla.org/projects/intl/UniversalCharsetDetection.html |
| 54 | + # for further detail. |
| 55 | + self.typical_distribution_ratio = None |
| 56 | + self._done = None |
| 57 | + self._total_chars = None |
| 58 | + self._freq_chars = None |
| 59 | + self.reset() |
| 60 | + |
| 61 | + def reset(self): |
| 62 | + """reset analyser, clear any state""" |
| 63 | + # If this flag is set to True, detection is done and conclusion has |
| 64 | + # been made |
| 65 | + self._done = False |
| 66 | + self._total_chars = 0 # Total characters encountered |
| 67 | + # The number of characters whose frequency order is less than 512 |
| 68 | + self._freq_chars = 0 |
| 69 | + |
| 70 | + def feed(self, char, char_len): |
| 71 | + """feed a character with known length""" |
| 72 | + if char_len == 2: |
| 73 | + # we only care about 2-bytes character in our distribution analysis |
| 74 | + order = self.get_order(char) |
| 75 | + else: |
| 76 | + order = -1 |
| 77 | + if order >= 0: |
| 78 | + self._total_chars += 1 |
| 79 | + # order is valid |
| 80 | + if order < self._table_size: |
| 81 | + if 512 > self._char_to_freq_order[order]: |
| 82 | + self._freq_chars += 1 |
| 83 | + |
| 84 | + def get_confidence(self): |
| 85 | + """return confidence based on existing data""" |
| 86 | + # if we didn't receive any character in our consideration range, |
| 87 | + # return negative answer |
| 88 | + if self._total_chars <= 0 or self._freq_chars <= self.MINIMUM_DATA_THRESHOLD: |
| 89 | + return self.SURE_NO |
| 90 | + |
| 91 | + if self._total_chars != self._freq_chars: |
| 92 | + r = (self._freq_chars / ((self._total_chars - self._freq_chars) |
| 93 | + * self.typical_distribution_ratio)) |
| 94 | + if r < self.SURE_YES: |
| 95 | + return r |
| 96 | + |
| 97 | + # normalize confidence (we don't want to be 100% sure) |
| 98 | + return self.SURE_YES |
| 99 | + |
| 100 | + def got_enough_data(self): |
| 101 | + # It is not necessary to receive all data to draw conclusion. |
| 102 | + # For charset detection, certain amount of data is enough |
| 103 | + return self._total_chars > self.ENOUGH_DATA_THRESHOLD |
| 104 | + |
| 105 | + def get_order(self, byte_str): |
| 106 | + # We do not handle characters based on the original encoding string, |
| 107 | + # but convert this encoding string to a number, here called order. |
| 108 | + # This allows multiple encodings of a language to share one frequency |
| 109 | + # table. |
| 110 | + return -1 |
| 111 | + |
| 112 | + |
| 113 | +class EUCTWDistributionAnalysis(CharDistributionAnalysis): |
| 114 | + def __init__(self): |
| 115 | + super(EUCTWDistributionAnalysis, self).__init__() |
| 116 | + self._char_to_freq_order = EUCTW_CHAR_TO_FREQ_ORDER |
| 117 | + self._table_size = EUCTW_TABLE_SIZE |
| 118 | + self.typical_distribution_ratio = EUCTW_TYPICAL_DISTRIBUTION_RATIO |
| 119 | + |
| 120 | + def get_order(self, byte_str): |
| 121 | + # for euc-TW encoding, we are interested |
| 122 | + # first byte range: 0xc4 -- 0xfe |
| 123 | + # second byte range: 0xa1 -- 0xfe |
| 124 | + # no validation needed here. State machine has done that |
| 125 | + first_char = byte_str[0] |
| 126 | + if first_char >= 0xC4: |
| 127 | + return 94 * (first_char - 0xC4) + byte_str[1] - 0xA1 |
| 128 | + else: |
| 129 | + return -1 |
| 130 | + |
| 131 | + |
| 132 | +class EUCKRDistributionAnalysis(CharDistributionAnalysis): |
| 133 | + def __init__(self): |
| 134 | + super(EUCKRDistributionAnalysis, self).__init__() |
| 135 | + self._char_to_freq_order = EUCKR_CHAR_TO_FREQ_ORDER |
| 136 | + self._table_size = EUCKR_TABLE_SIZE |
| 137 | + self.typical_distribution_ratio = EUCKR_TYPICAL_DISTRIBUTION_RATIO |
| 138 | + |
| 139 | + def get_order(self, byte_str): |
| 140 | + # for euc-KR encoding, we are interested |
| 141 | + # first byte range: 0xb0 -- 0xfe |
| 142 | + # second byte range: 0xa1 -- 0xfe |
| 143 | + # no validation needed here. State machine has done that |
| 144 | + first_char = byte_str[0] |
| 145 | + if first_char >= 0xB0: |
| 146 | + return 94 * (first_char - 0xB0) + byte_str[1] - 0xA1 |
| 147 | + else: |
| 148 | + return -1 |
| 149 | + |
| 150 | + |
| 151 | +class GB2312DistributionAnalysis(CharDistributionAnalysis): |
| 152 | + def __init__(self): |
| 153 | + super(GB2312DistributionAnalysis, self).__init__() |
| 154 | + self._char_to_freq_order = GB2312_CHAR_TO_FREQ_ORDER |
| 155 | + self._table_size = GB2312_TABLE_SIZE |
| 156 | + self.typical_distribution_ratio = GB2312_TYPICAL_DISTRIBUTION_RATIO |
| 157 | + |
| 158 | + def get_order(self, byte_str): |
| 159 | + # for GB2312 encoding, we are interested |
| 160 | + # first byte range: 0xb0 -- 0xfe |
| 161 | + # second byte range: 0xa1 -- 0xfe |
| 162 | + # no validation needed here. State machine has done that |
| 163 | + first_char, second_char = byte_str[0], byte_str[1] |
| 164 | + if (first_char >= 0xB0) and (second_char >= 0xA1): |
| 165 | + return 94 * (first_char - 0xB0) + second_char - 0xA1 |
| 166 | + else: |
| 167 | + return -1 |
| 168 | + |
| 169 | + |
| 170 | +class Big5DistributionAnalysis(CharDistributionAnalysis): |
| 171 | + def __init__(self): |
| 172 | + super(Big5DistributionAnalysis, self).__init__() |
| 173 | + self._char_to_freq_order = BIG5_CHAR_TO_FREQ_ORDER |
| 174 | + self._table_size = BIG5_TABLE_SIZE |
| 175 | + self.typical_distribution_ratio = BIG5_TYPICAL_DISTRIBUTION_RATIO |
| 176 | + |
| 177 | + def get_order(self, byte_str): |
| 178 | + # for big5 encoding, we are interested |
| 179 | + # first byte range: 0xa4 -- 0xfe |
| 180 | + # second byte range: 0x40 -- 0x7e , 0xa1 -- 0xfe |
| 181 | + # no validation needed here. State machine has done that |
| 182 | + first_char, second_char = byte_str[0], byte_str[1] |
| 183 | + if first_char >= 0xA4: |
| 184 | + if second_char >= 0xA1: |
| 185 | + return 157 * (first_char - 0xA4) + second_char - 0xA1 + 63 |
| 186 | + else: |
| 187 | + return 157 * (first_char - 0xA4) + second_char - 0x40 |
| 188 | + else: |
| 189 | + return -1 |
| 190 | + |
| 191 | + |
| 192 | +class SJISDistributionAnalysis(CharDistributionAnalysis): |
| 193 | + def __init__(self): |
| 194 | + super(SJISDistributionAnalysis, self).__init__() |
| 195 | + self._char_to_freq_order = JIS_CHAR_TO_FREQ_ORDER |
| 196 | + self._table_size = JIS_TABLE_SIZE |
| 197 | + self.typical_distribution_ratio = JIS_TYPICAL_DISTRIBUTION_RATIO |
| 198 | + |
| 199 | + def get_order(self, byte_str): |
| 200 | + # for sjis encoding, we are interested |
| 201 | + # first byte range: 0x81 -- 0x9f , 0xe0 -- 0xfe |
| 202 | + # second byte range: 0x40 -- 0x7e, 0x81 -- oxfe |
| 203 | + # no validation needed here. State machine has done that |
| 204 | + first_char, second_char = byte_str[0], byte_str[1] |
| 205 | + if (first_char >= 0x81) and (first_char <= 0x9F): |
| 206 | + order = 188 * (first_char - 0x81) |
| 207 | + elif (first_char >= 0xE0) and (first_char <= 0xEF): |
| 208 | + order = 188 * (first_char - 0xE0 + 31) |
| 209 | + else: |
| 210 | + return -1 |
| 211 | + order = order + second_char - 0x40 |
| 212 | + if second_char > 0x7F: |
| 213 | + order = -1 |
| 214 | + return order |
| 215 | + |
| 216 | + |
| 217 | +class EUCJPDistributionAnalysis(CharDistributionAnalysis): |
| 218 | + def __init__(self): |
| 219 | + super(EUCJPDistributionAnalysis, self).__init__() |
| 220 | + self._char_to_freq_order = JIS_CHAR_TO_FREQ_ORDER |
| 221 | + self._table_size = JIS_TABLE_SIZE |
| 222 | + self.typical_distribution_ratio = JIS_TYPICAL_DISTRIBUTION_RATIO |
| 223 | + |
| 224 | + def get_order(self, byte_str): |
| 225 | + # for euc-JP encoding, we are interested |
| 226 | + # first byte range: 0xa0 -- 0xfe |
| 227 | + # second byte range: 0xa1 -- 0xfe |
| 228 | + # no validation needed here. State machine has done that |
| 229 | + char = byte_str[0] |
| 230 | + if char >= 0xA0: |
| 231 | + return 94 * (char - 0xA1) + byte_str[1] - 0xa1 |
| 232 | + else: |
| 233 | + return -1 |
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